Adaptive Loop-Bandwidth Control Algorithm for Scalar Tracking Loops

This paper presents a loop-bandwidth control algorithm for adaptive scalar tracking loops used in modern digital global navigation satellite system (GNSS) receivers. This algorithm modifies the noise bandwidth of the loop filter. The updated loop-bandwidth balances the signal dynamics and noise through a weighting function. The agility of the estimators defines the sensitivity of the algorithm against dynamics. This algorithm is applicable to the delay-, frequency- or phase-locked-loop (DLL, FLL, PLL) and to any order loop-filter, making it simpler to incorporate than other methods. The algorithm is first analyzed and evaluated in a software receiver. Second, it is implemented in an open software interface GNSS hardware receiver for testing in simulated scenarios with real-world conditions. The scenarios represent different dynamics and noise cases. The results show the algorithm's generic usability and advantage over fixed loop settings, while preserving minimum tracking jitter and stability.